The phone that is bad is a KX-T7230 and the other phones on the system are KX-T7220. I believe that they are digital. We have swapped the KX-T7230 with all the other phones and KX-T7230 is the only one with the tone problem. You believe this problem is caused in the cabnet and not the individual phone? We swapped the cords and handsets with two other phones and still same tone problem.